An elastic-plastic material model, with strain-hardening or -softening, and volumetric strains, implemented within a general-purpose finite-element system (SAVFEM TM ), is shown to reproduce the stress -strain relationships and localized to de-localized (brittle to ductile) changes in strain response that have long been observed in typical laboratory experiments on common porous rocks. Based on that validation of the implementation, SAVFEM TM is then used to create numerical simulations that reproduce the patterns of localized shear zones, and their growth history, that occur in experimental (physical) models of fold-fault systems in layered rocks. These simulations involve a progressive evolution of the mechanical state, illustrating a geometrically dominated type of localization behaviour. Part of the deformation simulated here represents a crestal graben system. Analysis of the evolving mechanical state in the system of simulated faults poses challenges to some longstanding ideas concerning the way that faults operate, suggesting the need for a new fault-process paradigm.
A pulsating sphere is located inside a thick concentric viscoelastic spherical shell, which is surrounded by an infinite acoustic medium. The space between the sphere and the shell is filled with the same acoustic medium. A shaped beam of axisymmetric spherical harmonic wave, emitted from the sphere, is transmitted through the shell to the outside medium. The shell is analyzed by use of elastic wave potentials. The emitted acoustic waves are transmitted to the external medium by coupling to the shell through continuity and boundary conditions at the inner and outer surfaces of the shell. The investigation shows that the radiated farfield pressure can be attenuated by as much as 10% through the use of stiff polymers.
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